1. Field of the Invention
This invention relates to construction forms for installing concrete, and more particularly, to a polyethylene concrete form with a keyway that receives a base of a clamp that locks the concrete form to a stake and also relates to a concrete form end connector.
2. Prior Art
Concrete forms form the retaining walls between which concrete is poured and held until the concrete sufficiently hardens for the forms to be removed. The concrete forms are historically made of wood or steel and more recently of extruded polyethylene as well documented by Pawlicki in U.S. Pat. No. 5,015,117 issued in 1991. Where wood could be reused only a few times, extruded polyethylene forms can be used repeatedly for years and, unlike steel forms, they are lightweight for ease in transporting them.
The polyethylene concrete form described by Pawlicki further included a dovetailed keyway in a side into which is received a base of a clamp that secures a stake to the form. The base and keyway were matched such that the base fit through the keyway opening in a first orientation and then when rotated distorted the keyway slightly at about 45 degrees rotation as the base is rotated 90 degrees, providing resistance to inadvertent counter rotation and consequent release of the base out of the keyway. The resistance through the base corners against the keyway during rotation is effective but tends to wear out the base corners prematurely. The base also matched the dove-tailed form of the keyway such that when the base is rotated into installed position, the base is in binding face to face contact with the dove-tailed portion of the keyway and the bottom of the base also is pushed against the back of the keyway. The clamp is thus secured tightly to the form extending orthogonally from the form.
Pawlicki also described end connectors for the polyethylene concrete forms. The end connectors included a pair of posts each with a circumferential rim matching a pair of holes when two connectors are oriented face to face, the rims sized slightly larger than the holes so the post must be urged for a degree of force into the hole with the rims being pushed past the hole, resulting in resistance to one connector falling out of connection with another connector.
It is an object of the present invention to provide a polyethylene concrete form with a keyway with parallel opposing sides, unlike the dove-tailed keyway of Pawlicki, in which may be received a clamp base without distorting the keyway or clamp base. To strengthen the keyway, it is further object that the form have at least one as a keyway brace extending from intermediate the back of the keyway to an opposite form side. It is a further object to provide a base sized and shaped to fit through the keyway opening in a first orientation and when rotated in the keyway is prevented from falling out of the keyway. It is another object that the clamp base is rotatable in the keyway without restriction by the keyway.